I am curious about this as well, not to push you somewhere else but KartPulse also has a forum and it seems to be more active if you wanted to post the question there as well if you haven’t already. I have neither and was considering both and spoke to Swedetech a little on the topic. What I gathered is that the TM is a very solid, fast engine, especially if worked by a builder. They are very reliable and parts are easy to get. The Modena engines are apparently very fast out of the box but I have heard from a couple of different sources that they aren’t as reliable and have had some failures. From what or how significant I don’t know. If I recall correctly, there were quite a few Modenas at Indy in masters and the top 2 were on them.